Moisture content determining device having a pressure-operated capacitor member



April 1968 J. G. LILLARD ETAL 3,377,553

MOISTURE CONTENT DETERMINING DEVi-CE HAVING A PRESSUREOPERATED CAPACITORMEMBER Original Filed Nov. 29, 1963 v 5 Sheets-Sheet 1 WATER REACTOR ZPRODUCT FILTER WATER A GITATOR A 0 32 DRIER/ q o o o o 30 F l G I "fl"(h AUTOMATIC 3 WEIGHER 64 58 36 @L G==I e0 56 PRESSED BALE 42 5 4E} 4- f,((o (1(0)) L38 I) BALING PRESS .3 54 TO STORAG E 68 52 (I PAC KAGINGPROGRA M MER INVENTORS. JAMES G.LILLARD, ARNOLD R. ZUBIK, BY

ATTORNEY,-

Apnl 9, 1968 J. G. LILLARD ETAL 3,

MOISTURE CONTENT DETERMINING DEVICE HAVING A PRESSUREOPERATED CAPACITORMEMBER Original Filed Nov. 29, 1963 5 Sheets-Sheet 7.

RUBBER "RUBBER FIG- 2. FIG-3- IIIIIIIIIIII'I'.

PRESSED BALE HOLDING PERIOD FIG- 5- 1 INVENTORS.

' JAMES G. LILLARD, 'sMLOwE-RED) ARNOLD R. ZUBIK,

M $11416 FIG- 6- ATTORNEY.

April 9, 1968 .1. s. LILLARD ETAL 3,377,553

MOISTURE CONTENT DETERMINING DEVICE HAVING A Ofiginal Filed Nov.

PRESSURE-OPERATED CAPACITOR MEMBER 2.9. I

5 Sheets-Sheet F'l G 8 MD MR T A NL E L Vu W G S E M A J BY A RNOL o R zu B K ATTORNEY.

J. G. LILLARD ETAL April 9, 1968 3,377,553 MOISTURE CONTENT DETERMININGDEVICE HAVING A v PRESSURE-OPERATED CAPACITOR MEMBER Original Filed Nov.29, 1963 5 Sheets-Sheet 4 RUBBER BALE F IG l I INVENTORS. JAMESG-LILLARD, 'A RNOLD R- ZUBIK,

MJ T 'M ATTORNEY- Apnl 9, 1968 .1. cs. LILLARD ETAL 3,377,553

MOISTURE CONTENT DETERMINING DEVICE HAVING A PRESSURE-OPERATED CAPACITORMEMBER Original Filed Nov. 29, 1963 5 Sheets-Sheet INVENTORS.

JAMES G- LILLARD BY ARNOLD R. ZUBIK,

M aw

ATTORNEY.

mm m Y W :35 o wuzm niwm H Em I no D- mv h om mm N. mv h m Y W W T A u ww u mm 6 mm om g 3 a d om MN United States Patent 3,377,553 MOISTURECONTENT DETERMINING DEVICE HAVING A PRESSURE-OPERATED CAPACI- TOR MEMBERJames G. Lillard and Arnold R. Zubik, Baytown, Tex., assignors, by mesneassignments, to Esso Research and Engineering Company, Elizabeth, N.J.,a corporation of Delaware Continuation of application Ser. No. 326,826,Nov. 29, 1963. This application July 20, 1966, Ser. No. 566,713 1 Claim.(Cl. 324-61) This application is a continuation of application Ser. No.326,826, filed Nov. 29, 1963, now abandoned.

This invention-relates to the measurement of the moisture content ofparticulate material. More particularly, this invention is a method andsystem for accurately measuring the moisture content of bales of rubberunder pressure.

During the processing of certain materials, the final product is placedin packages in the for-m of bales of the product. The processing oftenrequires the use of Water or other volatile materials. Most of the wateror other volatile materials are removed during the process so that onlya small amount of water remains in the final product. The purchaser ofthe final product usually requires that the moisture content of thefinal product be less than a predetermined amount. Therefore, it isdesirable for the producer of the product to measure the moisturecontent of each bale of the product to make certain the moisture contentdoes not exceed the predetermined amount.

As a specific example, in the production of bales of Butyl rubber, aslurry of rubber in water is conducted to a filter to remove most of thewater. Some of the water, however, remains trapped inthe rubber. Therubber in the form of loose cakes is fed from the filter to a dryerwhere most of the remaining water is removed. The rubber is then brokenup into particles of rubber by mechanical action, automatically weighed,and then pressed into the form of bales in a baling press. The resultingbales of rubber are conveyed to a packaging area where they are placedin packages for shipment to the buyer.

The moisture content of the rubber must be determined to make certainthat the moisture content does not exceed the predetermined amount. Ifthe moisture content does exceed the predetermined amount, it is usuallydue to inefficient operation of the filter or dryer; and repairs must bemade to the filter or dryer.

The invention to be described herein is a method and system forautomatically and continuously measuring the moisture content of eachbale of rubber during the rubber producing process. In practicing theprocess, a predetermined amount of particulate rubber is fed into thebaling press. Pressure is then applied to the particulate rubber, andthe electrical capacitance of the resulting bale of rubber is measured.The electrical capacitance is a function of the moisture content of thebale of rubber. After the electrical capacitance of the bale of rubberis measured, the applied pressure is released; and the bale of rubber isremoved from the baling press.

The system includes the baling press which has a chamber for receivingthe particulate material. A pressureoperated member applies pressure tothe particulate material. An insulating dielectric is mounted on thepressureoperated member. A capacitor plate is mounted on the insulatingdielectric. The dimensions of the capacitor plate and the dimensions ofthe insulating dielectric are such that the capacitor plate is insulatedfrom the pressureoperated member. Means are provided for indicating thecapacitance of the particulate material under pressure.

The invention, as well as its many advantages, may be further understoodby reference to the following detailed description and drawings inwhich:

FIG. 1 is a schematic flow diagram of a butyl rubber finishing train;

FIGS. 2 through 10 show the sequence of operations for introducing theparticulate rubber into the baler, pressing the particulate rubber intothe form of a bale, and removing the bale of rubber from the baler;

FIG. 11 is an elevational view, partly in section, showing in moredetail a part of the capacitance measuring system;

FIGS. 12. and 13 are electrical diagrams useful in explaining theoperation of the capacitance measuring system; and I FIG. 14 is anelectrical schematic diagram illustrating the manner in which themoisture content of each bale of rubber is indicated.

Referring more specifically to FIG. 1, a flash tower 10 receives theproduct from a reactor (not shown). The reactor product is fed throughconducting line 12 to the flash tower 10. The reactor product consistsof particulate rubber in a liquid mixture of unreacted hydrocarbons andan inert carrier. The carrier and unreacted hydrocarbons are volatilizedby heat supplied by steam flowed through line 14 into the flash tower10. The volatilized carrier and unreacted hydrocarbons are removed fromthe flash tower 10 by means of overhead line 16. The rubber is suspendedin water in the flash tower 10. The water is fed to the flash tower 10by means of line 18. The rubber is kept suspended in the water by theagitator 20.

The rubber-in-water slurry flows from flash tower 10 through line 22 toa filter 24 such as an Oliver filter. The excess water is filtered offin the filter 24 and removed from the filter 24 by means of the waterline 26. The water removed from the filter 24 may be discarded orrecycled to the process.

The rubber, now in the form of loose cakes of discrete particles ofassorted sizes, is fed from the filter 24 through line 28 to a dryer 30.Hot air at a carefully controlled temperature and rate is passed throughthe rubber cakes to vaporize and carry off most of the remaining water.The conditions employed are dependent upon the rate of production andthe molecular weight of the reactor product and the efliciency ofperformance of the filter 24. These factors and the conditions of thedryer operation determine the moisture content of the product emergingfrom the dryer 30.

The product of the dryer 30 is fed through chute '32 to the conveyer 34.The product is mechanic-ally shredded as it passes through chute 32 andis carried by conveyer 34 to the automatic weigher 36. The shreddeddryer prod uct consists of particles of rubber of different thicknesses,different densities, and different void volumes.

When the desired weight of particulate rubber has been fed to theautomatic weigher 36, a signal is fed from the automatic weigher 36through line 38 to the programmer 40. The chute 42 is then automaticallylowered, and the rubber is dumped into the baling press 44. When theautomatic weigher 36 is empty, the chute 42 is retracted. The programmer40 then feeds a signal through line 46 to a hydraulic ram 48. Thehydraulic ram 48 pushes the cover 50 over the top of baling press 44.

After the cover 50 has been placed over the top of baling press 44, theprogrammer 40 feeds a signal through line 52 to a main hydraulic ram 54.The main hydraulic ram 54. presses the particulate rubber contained inbailing press 44 into the form of a bale of rubber. The pressure on therubber is maintained for a predetermined period of time. During thispredetermined period of time at which pressure is maintained on therubber, the programmer 40 feeds a signal through line 56 to the moisturemeter 58. The moisture meter 58 then records the electrical capacitanceof the bale of rubber in baling press 44. The electrical capacitance ofthe bale of rubber is fed through line 3 60 to an artificial line 64.The signal from artificial line 64 is fed to the moisture meter 58.

After the moisture content of the bale of rubber under pressure has beenmeasured by moisture meter 58, the programmer 40 shuts off the moisturemeter 58. The

pressure on hydraulic ram 54 is then released, and ram 48 moves cover 50from the bailing press 44. The ram 54 is then again operated to removethe bale of rubber from the baling press 44. The cover 50 is then againmoved forward to push the bale of rubber from baling press 44 onto theconveyer 66.

The conveyer 66 carries the rubber bale to the packaging unit 68. Thepackaged rubber bale is fed by conveyer 70 to storage. The balingsequence is then repeated when the automatic weigher 36 is again filledwith a predetermined amount of particulate rubber.

The operating sequence of the automatic baling system of FIG. 1 is shownin more detail in FIGS. 2 through 10. FIG. 2 shows the particulaterubber receiving position of the baling press 44. The chute 42 is in thedown position, and the cover 50 is in the retracted position. FIG. 3shows the loose rubber in the baling press 44. In FIG. 3, the chute 42has been retracted.

Thereafter, the hydraulic farm 48 is operated to extend the cover 50into position to close the top of the baling press 44 as shown in FIG.4. The main hydraulic ram 54 is then actuated. The ram 54 presses theparticulate rubber at a predetermined pressure of, say, 1600 psi. toform a bale of rubber. This step is shown in FIG. 5.. The pressure ismaintained for a predetermined period of time of, say, seconds. Duringthis time period, the programmer (FIG. 1) operates the moisture meter 58to measure the capacitance of the rubber under pressure.

After the capacitance of the rubber is measured, the pressure on themain ram 54 is reduced to lower the main ram 54 a short distance topermit the bale to lower sufficiently to be free of the cover (FIG. 6).The cover 50 is then retracted -(FIG. 7). Thereafter, the main ram 54 isagain actuated to push the bale of rubber out of the chamber formed inthe baling press 44' (FIG. 8).

The hydraulic ram 48 is then extended, and the cover 50 moves the baleof rubber onto the conveyer 66 of FIG. 1. The step is shown in FIG. 9.

As shown in FIG. 10, a spray then coats the walls of the baling press 44and the cover to prevent sticking. The cycle is then repeated.

The wide divergence in dielectric constants between rubber and waterwill cause significant change in the capacitance of a capacitor havingrubber as its dielectric as the moisture content of the rubber varies.Referring to FIG. 11, a plate 72 constitutes one plate of the capacitorhaving the rubber bale as its dielectric. The upper portion of thestationary walls of the baling press 44 and the cover 50 constitute theother plate of the capacitor. The plate 72 is mounted on a block 74 ofphysically stable, nonconducting material by means of polypropylenebolts 75. The block 74 of physically stable, nonconducting materal is,in turn, mounted on the head member 76 of the main hydraulic ram 54 bymeans of polypropylene bolts 77.

The dimensions of the capacitor plate 72 and the dimensions of the block74 of the insulating dielectric are such that the capacitor plate 72 isinsulated from the head 76. The block 74 may suitably be polypropylene.Polypropylene is physically much more dimensionally stable underpressure than the rubber being pressed at the pressure and temperatureof the process.

The walls of the baling press 44 provide a chamber 78 having an open topinto which the particulate rubber is dumped and from which the pressedbale of rubber is ejected. In one application, the chamber 78 may havedimensions of 14 inches by 28 inches. The polypropylene block 74 mayhave dimensions of 14 inches by 28 inches by 2 inches. The dimensions ofplate 72 may be 10 inches -by 24 inches. The depth of the bale of rubberwhile under pressure may be about 6 inches.

A conductor 80 is connected to the plate 72 by means of a screw 81having a hole formed throughlits middle. A shield 82 surroundstheconductor 80. The shield 82 is at ground potential. The shield 82electrically connects all intimately touching metal, parts comprisingbaling press 44, ram head 76, and main ram 54 to the ground terminal andcase of the junction box 84. A coaxial cable including conductor 60 andsurrounding shield 86 extends from the bottom of junction box 84.

The moisture meter is a device taking advantage of the wide difierencein the dielectric constant of the water and the dielectric constant ofthe rubber. This difference causes a variation in the capacitance of acondenser of essentially fixed dimensions when the watercontent of 1 therubber changes. It can be shown mathematically that the water content ofthe rubber bale is in accordance with the formula:

where S=the percent of the scale of the moisture meter;

M=the capacitance differential represented by full scale deflect-ion;

l=the thickness of the rubber dielectric;

k=a proportionality constant;

u=a correction factor termed a cell constant to correct for end effectsof capacitors having low A/l ratios;

A=the area of the plate;

e =th6 dielectric constant of the water; and

e =the dielectric constant of the rubber.

The total capacitance measured is the sum. of the capacitances of therubber bale; the insulating block 74;

the electrical leads; and capacitors C C and C (FIGU A.'B in FIG. 12 isrepresented by Z in FIG. 13 and Z is the impedance of capacitor C Thecombined voltage drops across Z and Z mustequal E. When Z increases, Zconstitutes a larger portion of E. The 1.6 megacycle voltage 'E across Zis then a function of the measured capacitance and acts as a sourcevoltage to the diode 90, the filter capacitor C and the resistor R.

Current can pass through the diode 90 in one direction only and isproportional to E This current contains a 1.6 rnegacycle component, a 60cycle component, and, because of rectification a DC. component.Essentially all the 1.6 megacycle componentof the current flows ascurrent through the filter condenser. The 60 cycle component flowsthrough the resistor R:

I As shown in FIG. 14, the voltage E is compared with the voltage E froma reference circuit 92. The components of the reference circuit 92 arefixed as are all the components ofthe measuring circuit except themeasured capacitance of the baled rubber. The output of the referencecircuit 92 is fed to .an RF detector 24. The output from the detector 94is the voltage E The reference voltage E is fixed. The voltage -Eappear-ing on themeasuring side decreases approximately linearly withmeasured capacitance increases. These two voltages constitute two lowerarms of a bridge with the upper arms consisting of the referencecapacitor C and the self-p0sitioning capacitor C The unbalance .voltageE is amplified by amplifier 96 :and fed to the self-positioningmechanism until C returns the bridge to the balanced condition, causingE to become zero. A pen mechanism 98 is attached to a shaft of theself-positioning capacitor C and records the degree of unbalanceoriginally appearing in the bridge by the dilference between thevoltages E and E The value of the capacitance of the rubber bale is afunction of the difference between voltages E and E The moisture contentof the rubber bale is, in turn, a function of the capacitance.

We claim: 1. A system for use in indicating the moisture content of aparticulate material under pressure comprising: wall means forming achamber with an open top for receiving the particulate material;

a pressure-operated cover member movable horizontally from a retractedposition to a position to close the top of the chamber, said covermember and a portion of said chamber constituting a portion of one plateof a capacitor;

a hydraulic pressure-operated member mounted in the chamber to movevertically which supports the particulate material and applies pressureto the particu late material when actuated;

an insulating dielectric mounted on the pressure-operated member;

a capacitor plate mounted on the insulating dielectric,

the dimensions of the capacitor plate and the dimensions of theinsulating dielectric being such that the capacitor plate is insulatedfrom the pressure-operated member; and

electrical means operatively connected to each of said capacitor platesfor indicating the capacitance of the particulate material underpressure.

References Cited UNITED STATES PATENTS 2,231,035 2/1941 Stevens et al.3-24-61 2,520,394 8/ 1950 Franzen-Lutz et al. 324-65 v2393,1168 7/4961Burnette 3246 1 3,005,153 10/1961 Berkley et a1. 324-65 3,090,004 5/1963Breen et al. 3246l RUDOLPH V. ROLINEC, Primary Examiner.

WA LTER L. CARLSON, Examiner.

E. E. KUBASIEWICZ, Assistant Examiner.

1. A SYSTEM FOR USE IN INDICATING THE MOISTURE CONTENT OF A PARTICULATEMATERIAL UNDER PRESSURE COMPRISING: WALL MEANS FORMING A CHAMBER WITH ANOPEN TOP FOR RECEIVING THE PARTICULATE MATERIAL; A PRESSURE-OPERATEDCOVER MEMBER MOVABLE HORIZONTALLY FROM A RETRACTED POSITION TO APOSITION TO CLOSE THE TOP OF THE CHAMBER, SAID COVER MEMBER AND APORTION OF SAID CHAMBER CONSTITUTING A PORTION OF ONE PLATE OF ACAPACITOR; A HYDRAULIC PRESSURE-OPERATED MEMBER MOUNTED IN THE CHAMBERTO MOVE VERTICALLY WHICH SUPPORTS THE PARTICULATE MATERIAL AND APPLIESPRESSURE TO THE PARTICULATE MATERIAL WHEN ACTUATED; AN INSULATINGDIELECTRIC MOUNTED ON THE PRESSURE-OPERATED MEMBER; A CAPACITOR PLATEMOUNTED ON THE INSULATING DIELECTRIC, THE DIMENSIONS OF THE CAPACITORPLATE AND THE DIMENSIONS OF THE INSULATING DIELECTRIC BEING SUCH THATTHE CAPACITOR PLATE IS INSULATED FROM THE PRESSURE-OPERATED MEMBER; ANDELECTRICAL MEANS OPERATIVELY CONNECTED TO EACH OF SAID CAPACITOR PLATESFOR INDICATING THE CAPACITANCE OF THE PARTICULATE MATERIAL UNDERPRESSURE.